The test does not guage what you know, but your evaluation of what you know.

You were invited to choose a range aiming for a 90% chance of getting each question right.

The questions were chosen by professional researchers (not by me). The point is that they are questions to which most people have little idea what the exact answer is, but most people should be capable of estimating an answer. The questions are quite cunning; they refer to things which you some experience with. And that's exactly the type of estmating we have to do in real life.

It's up to you to choose a range which you think includes the correct answer. You were given a blank cheque (check) ... and how did you spend it?

If you really gave your self a 90% of chance of getting each one correct, then 94% of the time, you would get at least 8 correct.

This probably isn't what happened, though. We seem to be biased towards over confidence. Most people do shockingly badly; we know we don't know the exact answer, but we're pretty sure about approximately what the the correct answer is, and we're too proud to take the easy way out and guess that the answers are between 0 and 999,999.